The present invention relates to an air bag apparatus in which an air bag, disposed in the inside of a seat back is inflated in a cabin upon a vehicle side collision thereby protecting a side portion of an occupant.
An air bag apparatus for protecting a side portion of an occupant in a car is disclosed, for example, in Japanese Patent Unexamined Publication No. Hei. 10-53086 or in Japanese Patent Unexamined Publication No. Hei. 3-108564. Generally, such an air bag apparatus is provided with an air bag module which has a folded air bag, an inflator, etc. A conventional air bag apparatus 200 will be described in brief with reference to FIG. 3. FIG. 3 is a schematic perspective view showing an air bag apparatus disposed in a seat back and a state in which the air bag is inflated.
The aforementioned air bag module 201 is received in a module casing 202. The air bag module 201 is set up together with the module casing 202 in a seat back S2. When a car is run into at its side, that is, upon a side collision, a sensor detects this collision and a gas is generated by an inflator 201a thereby unfolding an air bag 204 so that an occupant is protected.
FIG. 1 is a sectional view taken along the line X--X in FIG. 3 and showing the inside of the module casing 202. In the conventional air bag module 201, the air bag 204 is set up as shown in FIG. 1.
That is, the air bag 204 is folded stepwise, while alternately turning back at opposite ends was repeated to a forward end portion 204b after a holder 201b for holding the inflator 201a was enclosed in a base end portion 204a.
When the air bag 204 is inflated, a propellant in the inflator 201a is ignited so that a gas is generated to be fed into the air bag 204 (see the arrows in FIG. 1). As a result, the air bag 204 is inflated thereby forcing a cover portion 202a of the module casing 202 to open as indicated by the two-dot chain line in FIG. 1. The air bag 204 is further inflated continuously so as to be inflated while rupturing a seam portion in the right portion of the seat back S2 (see FIG. 3). FIG. 2 is a side view typically showing the inflating process of the air bag 104. FIG. 2A shows an initial state of inflating; FIG. 2B shows a state after a predetermined time is passed from the start of inflating; and FIG. 2C shows a state after inflation is completed.
In the conventional air bag module 202, the air bag 204 is folded alternately so that the opposite sides of the folded air bag 204 superimpose on one another completely. Therefore, it is inevitable that the air bag 204 must be inflated gradually from the base end portion 204a side. There is the possibility that inflating might be obstructed a little by a certain time lag with respect to the time required for gas to reach the forward end portion 204b of the air bag 204, or obstructed by failure of the folds of the air bag 204 in the middle of inflating.
With respect to the inflating of the air bag 204, it is very important that the air bag can be inflated rapidly to respond instantaneously to a car side collision. Accordingly, not only the inflating of the air bag 204 needs to be performed as rapidly as possible but also secure inflation of the air bag 204 needs to be attained.
In addition, such an air bag apparatus gives priority to the protection of the chest or head of an occupant. Accordingly, the air bag in the air bag apparatus is required to be inflated in a comparatively high position, such as the chest level, of the occupant. To unfold the bag in a comparatively high position, such as at the chest level of the occupant, To unfold the bag in a comparatively high position, such as at the chest level of the occupant, conceivably the module is received in a high position of the seat back.
A side portion of the seat back is, however, generally designed so as to be thinner higher up the seat back for the purpose of the occupant's comfort when riding. Accordingly, if the module is received in a high position of the side portion of the seat back, there is a disadvantage in spoiling the occupant's comfortable feeling when riding. Accordingly, the module is required to be received in a position as low as possible in the side portion of the seat back.